The KT7 and KT7-RAID are identical except for the RAID controller and the additional 4 IDE devices it supports. The RAID is a good deal for people that have a need for more than 4 IDE devices. You don't have to use the RAID features to use the additional ATA-100 IDE channels. If you need additional HDD speed, the RAID 0 function of the board works well- my Maxtor drive without RAID 0 scores 2100 on the SiSoft Drive benchmark, and scores over 3600 when RAIDed with an identical drive. Definately a signifacnt increase in speed. Use RAID 1 (mirroring) if you have critical enterprise data to safegard in real-time (unlikely).
If you are looking now, pay the extra $10 for the KT7A-RAID, it is worth it.
Good luck.